1. Field of the Invention
The present invention relates to a disk driving apparatus and a manufacturing method thereof.
2. Description of the Related Art
A disk driving apparatus, which rotates and drives an optical disk to record and reproduce information on and from the optical disk, is required to accurately record and reproduce information while suppressing vibration generated during the driving operation of the disk.
Conventionally, there has been proposed a disk driving apparatus which is provided with a structure for reducing the vibration during the driving operation of the disk (see JP-A-11-328944, for example). The disk driving apparatus described in JP-A-11-328944 is shown in FIGS. 1 and 2.
The disk driving apparatus shown in FIGS. 1 and 2 includes a main frame 3 supported by a casing 2 through a member 1. The main frame 3 includes a spindle motor 5 for rotating a turn table 4 to which an optical disk D is fixed. The main frame 3 further includes a stepping motor 7 for reciprocally moving a pickup device 6 in the radial direction with respect to the optical disk D which rotates together with the turn table 4. The pickup device 6 moves in the radial direction with respect to the optical disk D being rotated to record and reproduce information. A sub-frame 9 is attached on the upper surface of the main frame 3 through elastic members 8, whereby vibration generated at the main frame 3 is transmitted to the sub-frame 9 through the elastic members 8.
According to the disk apparatus configured in this manner, although the vibration transmitted to the main frame 3 from the casing 2 is attenuated by the member 1, the vibration generated by the rotation of the spindle motor 5 is directly transmitted to the main frame 3. In particular, the vibration due to the imbalance of the optical disk D rotating together with the turn table 4 is likely generated at the main frame 3.
In the disk apparatus 1, since the sub-frame 9 has a resonance frequency vibrating at a phase in opposite to that of the main frame 3, the vibration of the sub-frame 9 is cancelled by the vibration of the main frame 3 and so the vibration of the sub-frame 9 is reduced near the resonance frequency.
The frequency of the sub-frame 9 vibrating at the phase in opposite to that of the main frame 3, that is, the resonance frequency of a dynamic vibration absorber constituted by the sub-frame 9 and the elastic members 8 is mainly determined by the masses and rigidities of the sub-frame 9 and the elastic members 8. Thus, of the vibrations generated at the time of the recording and reproduction of a disk, only vibration near a particular frequency can be reduced. Further, in recent years, it has been required to record and reproduce various kinds of disks by a single driving apparatus. In this case, a utilized rotation speed range of a spindle is likely spread. When rotating the spindle at such a wide utilized rotation speed range, there arises a problem, as an example, that it is difficult to entirely reduce the vibration of a frequency range of a constant width.